Effects of structural parameters on water film properties of transpiring wall reactor

Corrosion and salt deposition problems severely restrict the industrialization of supercritical water oxidation. Transpiring wall reactor can effectively weaken these two problems by a protective water film. In this work, methanol was selected as organic matter, and the influences of vital structural parameters on water film properties and organic matter removal were studied via numerical simulation. The results indicate that higher than 99% of methanol conversion could be obtained and hardly affected by transpiration water layer, transpiring wall porosity and inner diameter. Increasing layer and porosity reduced reactor center temperature, but inner diameter's influence was lower relatively. Water film temperature reduced but coverage rate raised as layer, porosity, and inner diameter increased. Notably, the whole reactor was in supercritical state and coverage rate was only approximately 85% in the case of one layer. Increasing reactor length affected slightly the volume of the upper supercritical zone but enlarged the subcritical zone.     

Mathematical model for coal conversion in supercritical water: reacting multiphase flow with conjugate heat transfer

Providing heat for supercritical water gasification (SCWG) of coal by coupling subsequent products oxidation in integrated supercritical water reactor (ISWR) provides an effective method for directional control of temperature field and avoids excessive hot spots caused by uniform heating. An exploratory numerical model incorporating particle-fluid flow dynamics, multispecies transport and thermal coupling between endothermic coal gasification and exothermic product oxidation was established to simulate the reacting multiphase flow process of coal conversion in a novel lab-scale ISWR. An eleven-lump kinetic model was proposed for the prediction of chemical reactions. And the thermal coupling relationship was described by conjugate heat transfer boundary conditions (BC). Detailed physical and chemical field distribution in ISWR were analyzed and influence factors were discussed. The results showed that oxidation of gas products as inner heat source could promote the gasification reaction with only slight or even little maximum temperature increase of the pressure-bearing wall. Coal feeding rate and oxygen supply method significantly affected the field distribution. The multi-injection compressed-air supply method provided a more uniform temperature field but would reduce heat transfer temperature difference. The carbon gasification efficiency (CGE) in the gasification zone could easily reach up to 97% under mild conditions (less than 650 °C).     

超临界二氧化碳干气密封相态分布规律与密封性能研究

以超临界二氧化碳干气密封为研究对象，分别以维里方程、Lucas方程描述二氧化碳真实气体效应、黏度的变化，在考虑阻塞流效应的同时，采用有限差分法对考虑离心惯性力效应的Reynolds方程与能量控制方程进行耦合求解，分析讨论了工况参数与槽形结构参数对其相态分布规律与密封性能的影响。研究表明：S-CO₂从密封端面进口至出口的流动过程中，如果工况参数设置合理，将由超临界态逐渐转变为气态，并不会出现液态；较低的进口压力、进口温度以及转速，均会容易导致潜在的凝结流动发生；相比于工况参数对相态分布的影响，槽形参数对相态分布的影响较小，近乎可以忽略；开启力除了随进口温度的升高而减小外，均随进口压力、转速、槽深、螺旋角的增大而增大；泄漏率随进口温度和转速的增大而减小，但其随进口压力、槽深、螺旋角的增大而增大。这些结果为进一步研究超临界二氧化碳干气密封提供了一定的支撑。     

超临界二氧化碳干气密封稳态性能研究

以超临界二氧化碳(S-CO_2)干气密封为研究对象,建立变黏度变密度雷诺方程,通过构建物性数据库的方式对黏度及密度进行处理,并采用有限差分法对控制方程进行求解,得到端面压力分布,并计算开启力、泄漏量、摩擦扭矩和气膜刚度等稳态性能参数。结果表明:随着压力、转速的增大,开启力、泄漏量、摩擦扭矩、气膜刚度等参数均增大;随着槽坝比和槽深的增加,开启力、泄漏量和气膜刚度均增大,摩擦扭矩减小;随着槽数的增加,各稳态性能参数均减小;将槽坝比控制在0.5～1的范围内,有助于提高密封稳定性。     

Simulation Study on Hydrogen-Heating-Power Poly-Generation System based on Solar Driven Supercritical Water Biomass Gasification with Compressed Gas Products as an Energy Storage System

Supercritical water gasification driven by solar energy is a promising way for clean utilization of biomass with high moisture content, but direct discharge of liquid residual causes energy waste and decreases energy efficiency. To reduce energy waste, a poly-generation system for hydrogen-rich gas production coupling heat supply and power generation based on supercritical water gasification of biomass driven by concentrated solar energy was established in this paper, which also provided a novel energy storage method to overcome the shortcomings of solar discontinuity. Thermodynamic model of the system was proposed and life cycle assessment(LCA) of the system was conducted. Influence of different parameters(temperature of 600℃ to 800℃, outlet temperature of heat exchanger of 42℃ to 56℃, biomass slurry concentration of 5% to 6.5%) on the gasification performance, energy and exergy efficiency, energy distribution and global warming potential(GWP) was discussed. The results indicated that hydrogen yield increased as gasification temperature increased since free radical reaction was enhanced which gas production reaction was classified into. Molar fraction of hydrogen increased as gasification temperature increased and reached 65.6% at 750℃. Energy and exergy efficiency of the system reached 74.84% and 34.87% at 700℃ and 600℃ respectively and that of gas production was 18.15% at 650℃, which was the highest. Increasing reaction temperature and decreasing biomass slurry concentration were effective ways to decrease GWP. Optimal operating parameter was reaction temperature of 650℃, outlet temperature of heat exchanger of 50℃ and biomass concentration of 5%.     

生物可降解PCL/PLA开孔发泡材料制备及吸油性能

以聚己内酯（PCL）为基体，添加不同含量聚乳酸（PLA）熔融共混制备具有不同分散相形态的PCL/PLA共混物，利用超临界二氧化碳（scCO₂）微孔发泡工艺制备不同发泡倍率和开孔率的PCL/PLA多孔材料用于吸油应用。针对边长3 mm正方体样品溶解度实验发现100 min后CO₂在PCL中已达到饱和吸附状态。PLA分散相含量的增加显著增大了PCL/PLA共混物泡孔密度，并使共混泡孔尺寸减小且分布更加均匀；发泡温度升高6℃，泡孔尺寸增大50%，发泡倍率增大38%，开孔率减小了20%。PCL/PLA开孔材料具有明显的亲油疏水性，发泡倍率越高，疏水性越好；针对花生油和硅油的吸油实验发现材料吸油率与发泡倍率和开孔率整体呈正比，实际吸油量高于理论计算值，10次循环吸油测试后样品吸油率仅降低8.5%，材料吸油量与油品特性黏度关系不大。     

超临界CO2环境中温度和流速对N80碳钢腐蚀行为的影响

目的研究超临界CO2环境中温度和流速对N80碳钢腐蚀行为的影响,探讨N80碳钢在超临界CO2环境中的腐蚀机制。方法利用高压釜进行失重和电化学测试,同时利用扫描电子显微镜(SEM)和X射线衍射仪(XRD)进行腐蚀形貌观察和腐蚀产物成分分析。结果当温度为40℃时,腐蚀速率最小,电化学阻抗随时间延长持续减小,此条件下并没形成FeCO3保护膜。升高温度导致腐蚀初期的腐蚀速率明显增大,然而腐蚀某个时刻后,电化学阻抗突然增大,意味着FeCO3保护膜的形成。温度越高,腐蚀24 h后的阻抗越大,产物膜越致密,保护性越好。另外,腐蚀失重速率随流速的增加而增大,电化学测试也表明流速越大,阻抗越小,腐蚀电流密度越大。SEM形貌分析表明,流体流动破坏了FeCO3膜的致密度,降低了其对N80碳钢基体的保护作用。结论尽管升高温度加速了N80碳钢的腐蚀,但却有利于保护性FeCO3膜的形成。温度越高,FeCO3膜越致密。流体流动破坏了保护性FeCO3膜的致密性,加速了N80碳钢腐蚀。     

应用于钠冷快堆的超临界二氧化碳动力转换系统研究

超临界二氧化碳（SCO₂）布雷顿循环由于高效、紧凑和可避免钠水反应等特性而成为钠冷快堆的理想动力转换系统。本文以1 200 MWe大型池式钠冷快堆为系统热源，钠回路温度及热负荷为循环系统运行边界，对比研究了不同SCO₂布雷顿循环系统性能和关键设备性能的变化规律。研究发现，级间冷却再压缩循环与钠冷快堆热源特性匹配性最佳，且循环效率最高（40.7%）。进而研究了不同运行参数对级间冷却再压缩循环效率的影响规律，给出了循环系统效率对各关键影响因素的敏感度，发现循环系统效率对冷端参数的敏感度最强，其次为分流比和透平入口参数，对主压缩机级间压比的敏感度最弱。